1. Field of the Invention
The present invention relates to a heat transport apparatus. In particular, the invention relates to an vapor-lift pump (bubble pump) type heat transport apparatus that uses an vapor-lift pump and requires no external motive power.
2. Description of the Related Art
Conventionally, thermosyphons (i.e., heat pipes using gravity) are used as heat transport apparatus that use no external motive power. However, thermosyphons are limited in heat transport directions; in particular, it is difficult to perform downward heat transport. In these circumstances, a heat transport apparatus using an vapor-lift pump has been developed as a new heat transport apparatus (refer to JP-A-2002-122392, for example). As shown in FIG. 1 of JP-A-2002-122392, this heat transport apparatus is equipped with a heat exchange circulating solution container for containing a heat exchange circulating solution whose temperature is increased to a high temperature and high-temperature vapor produced from the heat exchange circulating solution by a phase change. The heat exchange circulating solution container is provided with a solution outlet and a vapor-liquid two-phase fluid inlet, and a circulating solution transport pipe is connected to the solution outlet and the vapor-liquid two-phase fluid inlet. The circulating solution transport pipe includes a solution outflow pipe that is connected to the solution outlet, an intra-container pipe that penetrates through the heat exchange circulating solution container, and a vapor-liquid two-phase fluid inflow pipe that is connected to the vapor-liquid two-phase fluid inlet. The solution outflow pipe is provided with a sensible heat releasing heat exchanger and the vapor-liquid two-phase fluid inflow pipe is provided with a heating heat exchanger.
The conventional heat transport apparatus having the above configuration, which transports heat from a high-temperature heat source to a heat sink utilizing a density difference that occurs in the heat exchange circulating solution in the circulating solution transport pipe due to a vapor-liquid phase change of the circulating solution, enables heat transport in an arbitrary direction without using external motive power.
However, the conventional heat transport apparatus has problems that a maximum heat transport capacity is small, the heat resistance is large (i.e., the heat characteristics are poor), and heat transport is difficult with a small temperature difference.
Another problem is that when the heat load is light the circulation flow rate of the heat exchange circulating solution that circulates through the circulating solution transport pipe intermits to cause vibration.